Mesoproterozoic subduction under the eastern edge of the Kalahari-Grunehogna Craton preceding Rodinia assembly: The Ritscherflya detrital zircon record, Ahlmannryggen (Dronning Maud Land, Antarctica)
Mesoproterozoic subduction under the eastern edge of the Kalahari-Grunehogna Craton preceding Rodinia assembly: The Ritscherflya detrital zircon record, Ahlmannryggen (Dronning Maud Land, Antarctica)
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DOI：
10.1016/j.precamres.2013.07.006
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发表时间：
2013-10
影响因子：
3.8
通讯作者：
H. Marschall;C. Hawkesworth;P. Leat
中科院分区：
文献类型：
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作者：
H. Marschall;C. Hawkesworth;P. Leat
中元古代Ritscherflya超群∼2000m厚的碎屑和火山碎屑沉积岩堆位于东南极Dronning Maud陆地太古代Grunehogna克拉通东缘附近。这些沉积岩沉积在罗迪尼亚超大陆组装之前俯冲过程中形成的活跃火山弧附近。在这项研究中，我们研究了Ritscherflya超群Ahlmannryggen群和Jutulstraumen群所有组的碎屑锆石颗粒的内部分带和U-Pb年龄。结果表明，沉积的年龄分布以∼1130Ma为主要年龄峰，接近沉积岩的沉积年龄(∼11301107Ma)，有力地支持了边缘收敛环境中沉积物的沉积模式。Ritscherflya沉积岩锆石谱中年龄高达3445 Ma±17.7 Ma的较老的峰，也在Grunehogna克拉通基底的样品中发现，反映了卡拉哈里克拉通的构造-岩浆事件。中元古代火山弧部分位于太古代克拉通基底(∼2800~3450Ma)，另一部分位于晚古元古代地壳(∼1750Ma)。这一点从许多继承的太古代和元古界具有斯太尼时代边缘的锆石中可见一斑。因此，Ritscherflya锆石记录支持卡拉哈里-格伦霍格纳克拉通东缘的模型，该模型包括在Dronning Maud陆地碰撞之前具有活动大陆边缘的向内俯冲。碎屑沉积岩与火山碎屑物质的夹层有力地支持了一个非常接近火山源的解释。在与Rodinia组装有关的碰撞造山和与Gonwaana组装有关的泛非造山过程中，沉积岩受到了区域低级变质作用的影响。这从1086 Ma±14.4 Ma的锆石变质重结晶和指示新元古代晚期至显生代早期铅损失的许多颗粒的不整合中可见一斑。
The ∼2000 m thick clastic and volcaniclastic sedimentary rock pile of the Mesoproterozoic Ritscherflya Supergroup is located near the eastern margin of the Archaean Grunehogna Craton of Dronning Maud Land (East Antarctica). The sedimentary rocks were deposited proximal to an active volcanic arc formed during subduction prior to the assembly of the Rodinia supercontinent. In this study, we investigated internal zonation and U-Pb ages of detrital zircon grains from all formations of the Ahlmannryggen and Jutulstraumen groups of the Ritscherflya Supergroup. Our results show an age distribution with a dominant age peak at ∼1130 Ma, close to the sedimentation age of the sedimentary rocks (∼1130–1107 Ma), which strongly supports the model of deposition of the sediments in a convergent margin setting. Older peaks in the Ritscherflya sedimentary rock zircon spectrum with ages up to 3445 ± 7 Ma that were also identified in samples from the Grunehogna Craton basement reflect tectono-magmatic events in the Kalahari Craton. This provides further evidence for the Archaean and Proterozoic connection of the Grunehogna province to the African Kalahari Craton.Parts of the Mesoproterozoic volcanic arc were located on Archaean cratonic basement (∼2800–3450 Ma), whereas other parts tapped late Palaeoproterozoic crust (∼1750 Ma). This is evident from a number of inherited Archaean and Proterozoic cores in zircons with Stenian rims. The Ritscherflya zircon record, therefore, supports models of the eastern margin of the Kalahari-Grunehogna Craton that include inward subduction with an active continental margin prior to collision in Dronning Maud Land. The intercalation of the clastic sedimentary rocks with volcaniclastic materials strongly supports the interpretation of a very proximal volcanic source.The sedimentary rocks were affected by regional low-grade metamorphism during the collisional orogeny related to Rodinia assembly and during the Pan-African orogeny related to the assembly of Gondwana. This is evident from metamorphic recrystallisation of zircon at 1086 ± 4 Ma and from discordancy of many grains pointing to late Neoproterozoic to early Phanerozoic lead loss.